1. Field of the Invention
The present invention relates to an apparatus for automatically mounting and removing replacement pins to and from a mandrel attachment fixture which is to be mounted to a pipe expanding apparatus for pushing pipe expanding mandrels during heat exchanger pipe expanding operation.
2. Description of the Prior Art
Hitherto, arrangements of the type having a mandrel attachment fixture for replacement pin mounting for use in pipe-expanding mandrel pushing operation have been known. Examples of such arrangements are described in Japanese Utility Model Application Laid-Open Publication No. 61-092428 and Japanese Utility Model Application Laid-Open Publication No. 63-184630.
The arrangement described in the first mentioned publication, as FIG. 4 (b) shows, comprises a pin body 14 insertable into a mandrel receiving through-hole 13 formed in a attachment fixture 12, a collar-shaped stepped portion 16 formed at one end of the pin body 14 for abutment with a lower stepped portion 15 formed in a lower portion of the mandrel receiving through-hole 13 and having a diameter larger than the diameter of the pin body 14, and a locking portion 19 formed at one end of the pin body 14 for engagement with a locking member 17 for locking the pin body 14 to the attachment fixture 12 when the pin body 14 is fitted in the mandrel receiving through-hole 13.
It is noted that, in this prior art arrangement, the attachment fixture 12 is of a two-piece construction, that is, it has upper and lower members 12a, 12b. For the purpose of pin locking, the upper and lower members 12a, 12b are first parted from each other, and then the pin body 14 is inserted through the mandrel receiving through-hole 13 of the lower attachment fixture member 12b.
Then, the locking member 17 is fitted on the locking portion 19 of the pin body 14 projecting upward from the lower push attachment member 12b, whereby the bin body 14 is locked to the lower push attachment member 12b. Subsequently, the upper push attachment member 12a is removably fitted to the lower member 12b. In this way, the pin body 14 can be removably fitted in position. It is noted that mandrel receiving through-holes 13 are provided in plurality so that pin bodies 14 can be removably inserted in suitably selected through-holes 13.
The arrangement described in the latter mentioned publication, as FIG. 5 shows, includes a first locking portion (collar portion) 23 adapted to abut the inner wall or entry-side opening edge of a mandrel receiving through-hole 21 of a pattern plate (push attachment) 20 when a pin body 22 is inserted into the mandrel receiving through-hole 21, to thereby prevent the pin body 22 from moving upward, a tapered face 26 of a tapered cylindrical configuration formed at the forward end of the pin body 22, with a body portion 25 having a hollow interior portion 24 which is defined between the locking portion 23 and the tapered face 26, and a plurality of slits formed in spaced relation on the tapered face 26 and extending along the direction in which the pin body 22 is inserted. On the border between the tapered face 26 and the body portion 25 there is formed a second locking portion 28 having a reverse tapered slope relative to the tapered face 26.
According to this arrangement, it is possible to insert the pin body 22, with the top end or the tapered face 26 as the leading side, into the mandrel receiving through-hole 21 of the pattern plate 20 through the lower opening thereof, and to lock the pin body 22 to the mandrel receiving through-hole 21 through the locking portions 23, 28 of the pin body 22.
In either of the above mentioned prior art apparatuses, it is possible to freely change the arrangement of pin bodies to be suitably fitted into individual mandrel receiving through-holes, in various different patterns to match the arrangement of pipes to be expanded.